Last year we discovered an unexpected effect which we plan to study further this year. Apparently, exposure to waveforms having steep spectral skirts has the potential to induce short-term and long-term changes in some listeners' psychophysical tuning curves. After intermittent exposure (as many as 10-12 four-minute exposures per day, with numerous short breaks, for a period of about eight weeks) to a high-frequency band of noise, two subjects showed greatly altered forward-masking tuning curves. The changes--increased sensitivity for the on-frequency masker at some signal frequencies, decreased sensitivity for the high-frequency maskers at other signal frequencies-gradually recovered over a period of months at some signal frequencies, but for those closest to the low-frequency edge of the noise band, the changes appear to be permanent. In a follow-up experiment using three volunteer subjects, similar short-term (10 minute) changes in tuning could sometimes be induced with exposures of 30-40 minutes. This year we plan to study further the short-term (temporary) version of this effect examining such variables as duration of exposure, steepness of spectral skirt, and signal frequency.